Starcraft AI blog

Here is a table of how each CherryPi opening fared against each opponent, like the tables I made for other bots. Reading the code confirmed my inference that the learning files recorded opening build orders, not build orders switched to later in the game; see how CherryPi played.

Look how sparse the chart is—CherryPi was highly selective about its choices. It did not try more than 4 different builds against any opponent. It makes sense to minimize the number of choices so that you don’t lose games exploring bad ones, but you have to be pretty sure that one of the choices you do try is good. Where did the selectivity come from?

The opening “hydracheese” was played only against Iron, and was the only opening played against Iron. It smelled like a hand-coded choice. Sure enough, the file source/src/models/banditconfigurations.cpp configures builds by name for 18 of the 27 entrants. A comment says that the build order switcher is turned off for the hydracheese opening only: “BOS disabled for this specific build because the model hasn’t seen it.” Here is the full set of builds configured, including defaults for those that were not hand-configured. CherryPi played only builds that were configured, but did not play all the builds that were configured; presumably it stopped when it hit a good one.

I read this as pulling out all the stops to reach #1. They would have succeeded if not for SAIDA.

banditconfigurations.cpp continues and declares some properties for builds including non-opening builds. It looks like .validOpening() tells whether it can be played as an opening build, .validSwitch() tells whether the build order switcher is allowed to switch to it during the game, and .switchEnabled() tells whether the build order switcher is enabled at all.

The build orders themselves are defined in source/src/buildorders/. I found them a little hard to read, partly because they are written in reverse order: Actions to happen first are posted last to the blackboard.

The opening zve9poolspeed (I read “zve” as zerg versus everything) has the most red boxes in the chart—it did poorly against more opponents than any other. It may have been a poor choice to configure for use in so many cases. In contrast, zvz9poolspeed specialized for ZvZ was successful. It gets fast mutalisks and in general has a lot more strategic detail coded into the build.

They seem to have had expectations of the zvt2baseultra build against terran. It is configured for HannesBredberg, WillyT, and the default ZvT. It was in fact only tried against SAIDA. I didn’t notice anything that tells CherryPi what order to try opening builds in. Maybe the build order switcher itself contributes, helping to choose the more likely openings first?